Without being aware of it, Vernon Madison might become a footnote in constitutional law because he is barely aware of anything. For more than 30 years, Alabama, with a tenacity that deserves a better cause, has been trying to execute him for the crime he certainly committed, the 1985 murder of a police officer. Twice the state convicted him unconstitutionally (first excluding African Americans from the jury, then insinuating inadmissible evidence into the record). In a third trial, the judge, who during his time on the bench overrode more life sentences (six) than any other Alabama judge, disregarded the jury’s recommended sentence of life imprisonment and imposed the death penalty.

The mills of justice grind especially slowly regarding capital punishment, which courts have enveloped in labyrinthine legal protocols. As the mills have ground on, life has ground Madison, 68, down to wreckage. After multiple serious strokes, he has vascular dementia, an irreversible and progressive degenerative disease. He also is legally blind, his speech is slurred, he has Type 2 diabetes and chronic hypertension, he cannot walk unassisted, and he has dead brain tissue and urinary incontinence.

And he no longer remembers the crime that put him on death row for most of his adult life. This is why on Tuesday the Supreme Court will hear oral arguments about the constitutionality of executing him.

His counsel of record, Bryan A. Stevenson, head of the Equal Justice Initiative in Montgomery, Ala., says it was undisputed in the penalty phase of Madison’s third trial that he already “suffered from a mental illness marked by paranoid delusions.” Stevenson says that Madison, who has been mentally ill since adolescence and who over the years had been prescribed “numerous psychotropic medications,” cannot remember “numerous events” of the past 30 years, including “events from the offense to his arrest or to his trial,” and cannot remember the name of the police officer he shot.

The mere phrasing of the matter at issue — whether Madison is “competent to be executed” — induces moral vertigo. A unanimous three-judge panel of the U.S. Court of Appeals for the 11th Circuit held that Madison lacks the requisite competence because he lacks understanding of the connection between his crime and his execution. The question before the Supreme Court is whether executing Madison would violate the Eighth Amendment’s proscription of “cruel and unusual punishments.”

The court has said that “we may seriously question the retributive value of executing a person who has no comprehension of why he has been singled out and stripped of his fundamental right to life.” For many people, the death penalty for especially heinous crimes satisfies a sense of moral symmetry. Retribution — society’s cathartic expression of a proportional response to attacks on its norms — is not, however, the only justification offered for capital punishment. Deterrence is another. But by now this power is vanishingly small because imposition of the death penalty is so sporadic and glacial. Because the process of getting from sentencing to execution is so protracted, averaging 15 years, senescent people on the nation’s death rows are going to be problems as long as there is capital punishment.

Madison’s case compels us to focus on the death penalty in its granular reality: Assisting someone who is non-ambulatory, and bewildered because he is (in Stevenson’s phrase) “memory-disordered,” to be strapped down so an executioner can try to find a vein — often a problem with the elderly — to receive a lethal injection. Capital punishment is withering away because the process of litigating the administration of it is so expensive, and hence disproportionate to any demonstrable enhancement of public safety, but also because of a healthy squeamishness that speaks well of us.

Sixty years ago, Chief Justice Earl Warren wrote that the Eighth Amendment — particularly the idea of what counts as “cruel” punishments — “must draw its meaning from the evolving standards of decency that mark the progress of a maturing society.” Concerning which, two caveats are apposite: “Evolving” is not a synonym for “improving,” and a society can become, as America arguably is becoming, infantilized as it “matures.” That said, it certainly is true that standards of decency do evolve and that America’s have improved astonishingly since 1958: Think about segregated lunch counters and much else.

Conservatives have their own standards, including this one: The state — government — already is altogether too full of itself, and investing it with the power to inflict death on anyone exacerbates its sense of majesty and delusions of adequacy.

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George F. WillGeorge F. Will writes a twice-weekly column on politics and domestic and foreign affairs. He began his column with The Post in 1974, and he received the Pulitzer Prize for commentary in 1977. His new book, "The Conservative Sensibility," will release June 4, 2019. Follow